Patent reference 1 describes a thermal analysis apparatus used as a conventional heating apparatus for a gas chromatograph. In this thermal analysis apparatus, a sample is placed in a pyrolysis furnace in which a heater is used to elevate the temperature, and vapor phase components produced by heating the sample are analyzed. With this thermal analysis apparatus, when the pyrolysis furnace is heated by the heater, the vapor phase components are produced from volatile components of the heated sample. When the temperature of the pyrolysis furnace is further elevated, high molecular components of the sample are pyrolized to low molecular components, thereby producing mixed vapor phase components. As the sample is thus heated up incrementally, a heart-cut can be used to analyze gas phase components at an arbitrary temperature.